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    Thread: Blue excitor wire on alternator, low voltage, battery light

    1. Member crazynorweegian's Avatar
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      09-29-2011 09:04 PM #1
      I noticed that my battery light was on upon startup after I did a bunch of things to my car. I read a thread that recommended revving the engine to activate the alternator and get the light to go out. I already understand that the blue wire basically activated the alternator upon ignition.

      I tested the wire in that position and when the car was running before I revved it and I got a very low reading of only a couple volts. After revving the engine passed 1200 RPM, I checked again and it was above 12v.

      I did some research in other threads and on other sites and see that this is somewhat common for MKII vehicles. However, unless it is a matter of the wire being unplugged or missing, most people seem to just let it be and rev the engine. I consider that a temporary fix at best.

      Has anyone fixed this themselves or have any ideas?
      Stephen
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      09-29-2011 09:14 PM #2
      This happened to my g60 corrado after pressure washing the engine bay. I Haven't owned the car that long, but I've only pressured washed it once and it was def a result of that. I assumed I blew something with the voltage regulator and pretty much just need to replace the alternator. But I dont drive the car everyday...yet.

    3. 09-29-2011 10:57 PM #3
      are you checking at the alternator or the battery?

    4. Member crazynorweegian's Avatar
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      09-29-2011 11:51 PM #4
      Quote Originally Posted by kyle h. View Post
      This happened to my g60 corrado after pressure washing the engine bay. I Haven't owned the car that long, but I've only pressured washed it once and it was def a result of that. I assumed I blew something with the voltage regulator and pretty much just need to replace the alternator. But I dont drive the car everyday...yet.
      Yeah dude, you need to cover the alternator when you wash. I'd make fun of you, but I did the same thing. Disconnect the battery, remove the regulator, blow it out with compressed air, and let it sit for minimum 24 hours. Should be better if you caught it before you fried something.

      Quote Originally Posted by wed3k View Post
      are you checking at the alternator or the battery?
      I am getting about 14.2 at the alternator and about the same amount at the battery. My wiring and alternator are awesome, no problem there. I guess you guys don't really know what I am talking about. The alternator field is excited or activated by that small blue wire at the alternator. It is grounded to activate the battery light if no current is being originated at the alternator. Once it is, then the blue wire post on the alternator is switched to 12V+ and the light in the cluster goes out. However, for some reason mine just stopped going off by itself. I have to rev the engine so as to "jump start" the alternator so that it will excite its own field. The wire is supposed to be a switched 12v supply connected to the ignition, routed through the idiot light with a diode. I only have to raise the RPMs like 250 to get it to work, so I am curious if I am just not getting high enough startup RPMs or what.

      I was thinking of just disabling the idiot light by running another wire from the post to an ignition switched circuit with a diode inline so that it will do the same thing. Either that, or maybe a relay with the blue wire triggering the 12v+ to the post, since it appears that I am getting a small voltage.

      Has any other Corrado owner had this problem?
      Stephen
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      Corrados decay in a way that can only be measured using quantum physics
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    5. Member RedYellowWhite's Avatar
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      09-30-2011 03:00 AM #5
      I had some battery drain issues a while back, long story short I replaced the alternator but since then I have to rev the car just a tad to get the alt to start charging (ie. battery light to go out).

      I don't know why but definately didn't need to before
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    6. Member corradokyd's Avatar
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      09-30-2011 03:07 AM #6
      I had that issue with an old alt with my pg motor a while back. I always thought it was the alternator brushes or the generator it self. The blue wire from what I understand is a signal wire which has something to do with the alternator charging the battery. It is a common mk1 problem where they have charging problems and turns out being a bad signal to the fuse box from the alternator. somebody please tell me Im crazy...

    7. Member crazynorweegian's Avatar
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      09-30-2011 03:19 AM #7
      Quote Originally Posted by corradokyd View Post
      I had that issue with an old alt with my pg motor a while back. I always thought it was the alternator brushes or the generator it self. The blue wire from what I understand is a signal wire which has something to do with the alternator charging the battery. It is a common mk1 problem where they have charging problems and turns out being a bad signal to the fuse box from the alternator. somebody please tell me Im crazy...
      No, you're kyd, I'M crazy. lol

      Well, on a hunch, I stuck my battery on a charger on high for about 6 hours and got the sucker up to 13.3, ran it a few times, now I have no battery light on startup.... for now. Goddamned optimas....
      Stephen
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    8. Member MikkiJayne's Avatar
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      09-30-2011 09:19 AM #8
      Thats just how it is on some cars I think. The voltage behaviour is how its supposed to work. Most alternators fire up at idle, some need a few more RPM - my A6 needs about 1400, but it still charges fine. I don't consider it a problem, although if there is a fix I would be curious to know what it is
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    9. Member RedYellowWhite's Avatar
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      09-30-2011 09:55 AM #9
      Quote Originally Posted by MikkiJayne View Post
      Thats just how it is on some cars I think. The voltage behaviour is how its supposed to work. Most alternators fire up at idle, some need a few more RPM - my A6 needs about 1400, but it still charges fine. I don't consider it a problem, although if there is a fix I would be curious to know what it is
      Quote Originally Posted by dogger View Post
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    10. Member crazynorweegian's Avatar
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      09-30-2011 04:55 PM #10
      Quote Originally Posted by MikkiJayne View Post
      Thats just how it is on some cars I think. The voltage behaviour is how its supposed to work. Most alternators fire up at idle, some need a few more RPM - my A6 needs about 1400, but it still charges fine. I don't consider it a problem, although if there is a fix I would be curious to know what it is
      Well, try this. Put 12v+ straight from the battery over to the alternator exciter post (might want to put that inline diode just in case). If that solves it, then you have a weak signal somewhere. You can track it down, but I would probably just macguyver something. If I end up having to do that, I will post up some pictures here.
      Stephen
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    11. Member G0to60's Avatar
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      09-30-2011 05:10 PM #11
      I have this same problem. A few months ago my alt. went out. After I installed my new one this problem comes up intermittently. This morning I had to slightly rev the engine to get the light to go out but yesterday I had no issues. I haven't dug too deep into this (checked my connections between battery and alt.) but I have a hunch it might be my battery as it's getting a little old.

    12. Member crazynorweegian's Avatar
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      09-30-2011 07:51 PM #12
      It appears to have been my battery as well. I just needed a solid charge I guess. Only time will tell...
      Stephen
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      Black 1990 1.9L Stage 5 G60 - keeper
      Corrados decay in a way that can only be measured using quantum physics
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      09-30-2011 08:02 PM #13
      Maybe a new voltage reg?
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    14. Member sdezego's Avatar
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      09-30-2011 08:05 PM #14
      Quote Originally Posted by G0to60 View Post
      .. This morning I had to slightly rev the engine to get the light to go out but yesterday I had no issues.
      I have had to do this on every VW (Mk1s, MkIIs and Corrados) I have ever owned, no matter what.

      I assumed it had to do with the output amperage at idle. Yes, blue exciter wire energizes the Fields on the Alt, but if there is not enough voltage differential at low idle, then this will never be enough to flow past the Batt Light (Diode). As anal as I am , I just always accepted it.

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      10-12-2011 02:04 PM #15
      Reading back through this thread and having little more experience with the operation of my light (very little though). I wondered what the engine temperature is when we're starting the cars.

      If it's very cold, shouldn't the ISV increase the idle enough to have the alt light go out...automatically. I've removed my ISV, but I would imagine it would blip the idle high enough to make the light go out even if the engine was a bit hot on start.

      With all the ISV problems these cars have, could that be the leading issue? Again, very little experience with VWs of this generation, but on start (cold or hot) engines rarely start up and immediately maintain idle rpms.

    16. Member g60301's Avatar
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      10-12-2011 04:47 PM #16
      Kind of the same prob going on with my car, however I installed a used alt. the readings at start up is 12ish then a rev up jumps it to 13.5. I know its a little low but its used and god knows how old! But hope it last me a while till I get a brand new one or have mine rebuilt. No issue with the batt light though. I went ahead and changed the batt light on fruday for the hell of it, just to make sure it wasent blown

    17. Member TheBurninator's Avatar
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      10-12-2011 05:31 PM #17
      Quote Originally Posted by g60301 View Post
      Kind of the same prob going on with my car, however I installed a used alt. the readings at start up is 12ish then a rev up jumps it to 13.5. I know its a little low but its used and god knows how old! But hope it last me a while till I get a brand new one or have mine rebuilt. No issue with the batt light though. I went ahead and changed the batt light on fruday for the hell of it, just to make sure it wasent blown
      13.5 is about right for a VW alternator. Anything higher than 13.9-14 volts on a VW is odd and signs of a bad voltage regulator.
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    18. Member crazynorweegian's Avatar
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      10-12-2011 09:45 PM #18
      You should be able to tell the light is working by turning the ignition switch to the battery position. All dash lights should come on. That is like used car shopping 101...
      Stephen
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      10-12-2011 10:33 PM #19
      Quote Originally Posted by crazynorweegian View Post
      You should be able to tell the light is working by turning the ignition switch to the battery position. All dash lights should come on. That is like used car shopping 101...
      Guess it dosent work. I replaced the led in it with another one just to be safe but I guess somethings burned out somewhere. If I turn the key one notch the lights that should come on do minus the batt light.is there a fuse for it somewhere?

    20. Member crazynorweegian's Avatar
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      10-12-2011 11:02 PM #20
      Quote Originally Posted by g60301 View Post
      Guess it dosent work. I replaced the led in it with another one just to be safe but I guess somethings burned out somewhere. If I turn the key one notch the lights that should come on do minus the batt light.is there a fuse for it somewhere?
      Exciter will not work without the light functioning. I believe the bulb has to be the exact right one. I cannot remember, but I think the LED itself somehow works as the diode to keep the power running one way. I am talking out my butt, I never looked at the diagram, so this is all word vomit from other threads. Either way, you are looking at a wiring fault or a bulb fault. Start by doing a continuity test between the ring terminal at the alternator and the lead to the LED, then work back toward the engine bay until you find the break/ damage.

      I think my problem ended up being my battery, but it looks like my warranty might save me... this time.
      Stephen
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    21. Member g60301's Avatar
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      10-12-2011 11:11 PM #21
      Quote Originally Posted by crazynorweegian View Post
      Exciter will not work without the light functioning. I believe the bulb has to be the exact right one. I cannot remember, but I think the LED itself somehow works as the diode to keep the power running one way. I am talking out my butt, I never looked at the diagram, so this is all word vomit from other threads. Either way, you are looking at a wiring fault or a bulb fault. Start by doing a continuity test between the ring terminal at the alternator and the lead to the LED, then work back toward the engine bay until you find the break/ damage.

      I think my problem ended up being my battery, but it looks like my warranty might save me... this time.
      Thats what my buddy tech said. I was thinking in my head, how could a led tell the alt to start charging! Well thats how he basicly explained it to me. I took a bulb out of my spare cluster and replaced the batt light in my currently used cluster. Still nothing. Guess im gonna have to start testing $hit. He told me to rev it up to 4grand then the alt jumps up to good voltage.

    22. Member crazynorweegian's Avatar
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      10-13-2011 02:32 AM #22
      Yeah, I guess that works in a pinch. I would find the minimum RPM jump that works. Revving your car so hard when cold is murdering your engine.
      Stephen
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    23. Member crazynorweegian's Avatar
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      03-06-2012 04:50 PM #23
      Update: this problem went away with the elimination of vacuum leaks, boost leaks, and proper ignition timing.
      Stephen
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      03-06-2012 07:50 PM #24
      Quote Originally Posted by crazynorweegian View Post
      Update: this problem went away with the elimination of vacuum leaks, boost leaks, and proper ignition timing.
      That good to know. My was doing this, it was bc my aba-G60 setup years ago and my G60 injectors just worn out. Replace chip to 30# setup with new 30# injectors. Having a G60, your always checking things over, definely it's your daily. I noticed poor injectors causing this problem too, at times won't start on first try.

      I noticed it vacuum leak-idle will increase on digi-1. Not sure boost leak will cause? I if time is retard a little, it cause lower idle and need rev engine to activate the exciter wire.

    25. Member g60301's Avatar
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      03-06-2012 09:39 PM #25
      Same probably here, I've been too lazy to replace the ignitor wire though. I need to Rev mine past 3k then all lights get bright! . I'm watching this thread.

    26. Member g60301's Avatar
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      03-06-2012 09:42 PM #26
      Quote Originally Posted by crazynorweegian View Post
      Update: this problem went away with the elimination of vacuum leaks, boost leaks, and proper ignition timing.
      I highly sought it was vacuum related? That strange how a vacuum leak would not tell your alt to start charging. Just mo

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